Lesson #5 (summarized) - Classification of Eukaryotic vs. Prokaryotic

Linnaeus' Classification

  • Initially recognized only two kingdoms: animals and plants.
  • Micro-organisms necessitated further classification.
  • Microscopes enabled better understanding of cellular structures.

Classification of Living Things

  • Three domains:
    • Eubacteria: Kingdom Eubacteria, prokaryotic, cell walls with peptidoglycan, unicellular, autotroph or heterotroph (e.g., Streptococcus, Escherichia coli).
    • Archaea: Kingdom Archaea, prokaryotic, cell walls without peptidoglycan, unicellular, autotroph or heterotroph (e.g., methanogens, halophiles).
    • Eukarya: Kingdoms Protista, Fungi, Plantae, Animalia; eukaryotic.
      • Protista: Cell walls of cellulose in some; some have chloroplasts. Most unicellular; some colonial; some multicellular; autotroph or heterotroph (e.g., Amoeba, Paramecium, slime molds, giant kelp).
      • Fungi: Cell walls of chitin, multicellular, heterotroph (e.g., Mushrooms, yeasts).
      • Plantae: Cell walls of cellulose; chloroplasts, multicellular, autotroph (e.g., Mosses, ferns, flowering plants).
      • Animalia: No cell walls or chloroplasts, multicellular, heterotroph (e.g., Sponges, insects, fishes, mammals).

Domains of Life

  • Eubacteria contains Kingdom Eubacteria.
  • Archaea contains Kingdom Archaea.
  • Eukarya contains Kingdoms Protista, Animals, Plants, and Fungi.

Species Concept

  • Morphological Species Concept: Focuses on form and structure, comparing organisms and considering variations.
  • Biological Species Concept: Emphasizes the ability of organisms to breed and produce viable/fertile offspring.
  • Anatomical Evidence: Uses homologous bone structures to infer evolutionary relationships.
  • Physiological Evidence: Examines biochemistry, like protein and enzyme structures, to classify organisms (e.g., guinea pig insulin).
  • Phylogenetic Species Concept: Focuses on evolutionary relationships and DNA sequences (e.g., red panda related to raccoons).

Prokaryotes

  • Single-celled, lack membrane-bound organelles and a nucleus.
  • DNA in nucleoid region.
  • Smallest, dominant life forms.
  • Include Eubacteria and Archaea.
  • Some bacteria are pathogens, causing diseases (e.g., strep throat, salmonella).
  • Key roles in ecosystems: decomposers, nutrient recyclers, and producers of atmospheric oxygen.
  • Mutualistic relationships (e.g., bacteria in human intestines producing vitamins).
  • Produce antibiotics.

Eukaryotes

  • Multicellular with membrane-bound organelles and a nucleus.
  • Internal membranes from folded cell membrane of ancestral prokaryotes.
  • Mitochondria and chloroplasts originated via endosymbiosis.
  • Endosymbiosis: One single-celled organism lives within another organism. Mitochondria and chloroplasts have their own chromosomes (DNA).